Mcast = Multi-cast.
this tool will broadcast the bootloader and new firmware across your network using a multicast address (meaning and computer on your network will see this traffic). The mag box listens on a multicast broadcast rather than an IP address it gets from your network.
I tried updating my firmware using this tool since I was unable to via USB but for some reason I was only able to get the bootloader updated but the firmware didn't.
I found that my USB stick wasn't working properly, and tried another one, with that the firmware updated.
You probably don't need to update via this method.
